Semiconductor nanocrystals, also called quantum dots, are a unique type of nanoparticle, which exhibit size-dependent properties that are not observed in either their discrete atom or bulk phase counterparts. These properties include, for example, narrow, tunable emission spectra, enhanced magnetic properties, altered electrical or optical activity, altered chemical or biological activity, and extended fluorescence lifetimes and enhanced emission and photostability relative to traditional organic fluorophores. Semiconductor nanocrystals are currently under investigation for applications in fundamental scientific research efforts to potential applications in the optoelectronics, high-density memory, lasing media, solar cell, and biolabeling industries, among others.
Semiconductor nanocrystals of the prior art, while exhibiting remarkable and commercially relevant properties, are vulnerable to a number of degradation processes, such as for example, oxidation, hydration, or photo-ionization. Among these, are processes that directly attack the interior of the nanoparticles such as oxidation, and processes that attack or modify the surfaces of the nanoparticles. Interior-attack processes over time may irreparably modify the constituent materials and thereby eliminate their functionality altogether. Surface-attack and surface-modification processes result from interactions of the surfaces of the nanoparticles with surrounding media. For example, temperature, electrolyte concentration, and pH in surrounding aqueous media may contribute to nanocrystal degradation.